It is known to employ a swingable draw-pin-retaining arm in combination with a specially constructed hitch draw-pin (U.S. Pat. No. 2,654,613 to Blair et al). But is is not known to provide a swingable-arm unit that is easily attachable without drilling to a conventional clevis-type hitch and is swingable to retainingly overlie a conventional draw-pin therein. It is the principal object of the present invention to provide such a unit. Other objects and advantages will become apparent as the following detailed description proceeds.